1. Field of the Invention
This invention relates to a vehicle slip angle measuring method and a device therefor suitable for a vehicle having a four-wheel steering system.
2. Description of the Related Art
A four-wheel steering system for steering the front and rear wheels of a vehicle at the time of turning the vehicle to enhance the turning performance and steering stability of the vehicle is typically operable to steer the rear wheels by an angle corresponding to the vehicle velocity and the steering angle of the front wheels. Also known is a four-wheel steering system which detects the vehicle centroid slip angle, and steers the front and rear wheels to set the slip angle to zero. According to the slip angle zeroing control, the vehicle can be directed in the vehicle traveling direction even at the turning time. This is convenient for driving.
Conventionally, for example, an optical non-contact type ground speed meter (vector speed meter) is used to detect the vehicle centroid slip angle. In this case, the vehicle centroid slip angle is derived from the longitudinal velocity and lateral velocity of the vehicle measured by the ground speed meter. However, the ground speed meter is lowered in the detection precision depending on the road surface condition, and is large in size and expensive. Therefore, the practical applications of the slip angle zeroing control using the ground speed meter in commercially available vehicles is low.